THE NERVOUS SYSTEM 303
the anterior division of the combined 08 and Dl, from the union the median (M.N.) and ulnar (U.N.) nerves result. There is thus no distinct separation of outer and inner cords as in Man. The posterior divisions from the sixth cervical to first dorsal nerves unite to form a posterior cord from which four subscapular (ILS.N., L.S. and Lo.S.), the circumflex (C.N.) and musculo-spiral (M-S.N.) nerves arise. The internal cutaneous (I.C.N.), lesser internal cutaneous (L.I.C.) and coraco-brachial nerves (C.B.N.) arise from representatives of the outer and inner cords.
In the Gorilla, according to Eisler (442) and Hepburn (83) the anterior divisions of C5 and C6 form the musculo-cutaneous nerve, which communicates with the median nerve. The anterior divisions of 06, 07, 08 and Dl form the median nerve. The anterior divisions of 07, 08 and Dl form the ulnar nerve.
The posterior divisions of 05 to Dl form a posterior cord, whose branches are as in the Chimpanzee. In the Orang the arrangement approaches most closely to that in Man.
BEANCHES OF THE PLEXUS.
The suprascapular nerve (n. dorsalis scapulae) -arises from 04 and 05 in the Gorilla, from 05 in the Gibbons and some Chimpanzees, and from 05 and 06 in other Chimpanzees and the Orang. Its course and branches are as in Man.
Anterior Thoracic Nerves.—These arise separately or from a single trunk. They are distributed to the pectoral muscles, and a loop connects them as in Man.'
The long thoracic nerve is similar to that in Man.